In prior art seats of the above type, the cover of the seat back entirely covers the front face of the safety device casing, the cover having a tearable seam in corresponding relationship to said front face.
The above prior art seats have the following drawbacks:
it can be difficult to position the tearable seam in the cover perfectly relative to the front face of the casing: if it is not positioned correctly, the safety device can malfunction or even not function at all if the vehicle suffers an accident, and PA1 it is necessary to validate correct operation of the safety device for each design of seat back cover, because the operation of said safety device involves tearing said cover: given the large number of cover designs possible for each vehicle model, this entails a very large number of costly tests. PA1 the exit passage in the front face of the casing is near the lateral wall of the casing, the two edges of the exit passage being attached one to the side wall of the casing and the other to a closure wall that is part of the front face of the casing and which can be raised relative to a fixed part of said casing to open the exit passage, the first edge of the slot in the cover being fixed to the side wall of the casing and the second edge of said slot being fixed to the closure wall; PA1 the side wall of the casing has a mobile part that carries the first edge of the slot in the cover and which is adapted to move away from the fixed part of the casing, compressing the upholstery of the seat back and widening the exit passage, when the bag of the safety device inflates; PA1 the exit passage in the front face of the casing is bordered by a channel attached to the side wall of the casing and opens laterally towards the outside of the seat back, the first edge of the slots in the cover being engaged in said channel and this first edge being provided with retaining means that co-operate with complementary retaining means in the channel to hold said first edge in said channel; PA1 the channel along the exit passage in the front face of the casing is formed in one piece with the plastics material side wall of the casing, said channel having a substantially U-shape cross-section with an outside wall, an inside side wall formed by the side wall of the casing and a back wall joining said outside and inside side walls; PA1 the channel along the exit opening in the casing has a substantially U-shape cross-section with an outside side wall away from the casing, an inside side wall nearer said casing and a back wall joining said outside and inside side walls, the outside side wall including inwardly projecting rims that constitute said complementary retaining means, the retaining means attached to the edge of the cover comprising a substantially J-section flexible section which is open towards the outside of the seat back and which has, on the one hand, an inside branch fixed to the edge of the cover and, on the other hand, an outside branch that hooks behind the projecting rims on the outside side wall of the channel; PA1 the second edge of the slot in the cover is mounted on a flat section that extends parallel to the front face of the casing and is fixed to the closure wall of said front face; PA1 the slot in the cover is extended beyond the casing of the safety device by two end portions on respective opposite sides of said casing, said two end portions being adapted to open when the bag of the safety device inflates; PA1 at least one edge of the slot in the cover is free along at least part of one end portion of said slot in the vicinity of the casing; PA1 the two edges of the exit passage in the front face of the casing are attached one to the side wall of the casing and the other to a closure wall that is part of the front face of the casing and which can be raised relative to a fixed part of said casing on opening the exit passage, the first edge of the slot in the cover being mounted, at the level of at least one end portion of said slot, on a section that is attached to the side wall of the casing; PA1 the two edges of the exit passage in the front face of the casing are attached one to the side wall of the casing and the other to a closure wall that is part of the front face of the casing and which can be raised relative to a fixed part of said casing on opening the exit passage, the second edge of the slot in the cover being mounted, at the level of at least one end portion of said slot, on a section attached to the closure wall of the front face of the casing; PA1 the front face of the casing of the safety device is covered by a cover section attached to said casing and having an exit passage which extends in a longitudinal direction substantially parallel to the slot in the cover and which is disposed in corresponding relationship to the exit passage in the front face of the casing, the cover section further including first and second longitudinal parts disposed on respective opposite sides of the exit passage of said section, the first longitudinal part of the cover section being fixed to the first edge of the slot in the cover, the second longitudinal part of said section being fixed to the second edge of the slot in the cover, and the two longitudinal parts of the cover section being joined together by at least one flexible connection disposed at one end at least of the exit passage of the section, said exit passage being normally closed and said flexible connection being adapted to allow said exit passage to open and at the same time as the exit passage in the front face of the casing; PA1 the exit passage in the front face of the casing is near the side wall of said casing, the two edges of said exit passage being attached one to the side wall of the casing and the other to a closure wall that is part of the front face of the casing and which can be raised relative to a fixed part of said casing on opening the exit passage of the casing, the second longitudinal part of the cover section being fixed to the closure wall and the first longitudinal part of the cover section forming a channel along the side wall of the casing that is open laterally outwards of the seat back, the first edge of the slot in the cover being engaged in said channel, and said first edge being provided with retaining means that co-operate with complementary retaining means in the channel to hold said first edge in said channel; PA1 the cover section has first and second lateral edges extending substantially in said longitudinal direction between two end edges, the first lateral edge including said channel of the section and the cover section further including a thin film that can be bent and which extends from the channel to the second lateral edge of the section, said thin film having a U-shape slot that has a longitudinal central part and two lateral branches extending towards the second lateral edge of the section as far as two ends at the level of which the thin film is folded on itself along two fold lines each of which extends between one end of the U-shape slot and one end edge of the cover section, said two folding lines and the U-shape slot delimiting said first and second longitudinal parts of the cover section and the fold lines constituting said flexible connection, the first longitudinal part of the section including said channel and being disposed directly against the front face of the casing, the second longitudinal part of the section including the second lateral edge of said section and also including a tongue that is delimited by the U-shape slot, said second longitudinal part of the section being folded over the first longitudinal part substantially at 180.degree., said tongue being fixed directly against the closure wall of the front face of the casing and extending away from the first and second lateral edges of the section, uncovering a central opening that is disposed above the exit passage in the front face of the casing and which is covered by the second longitudinal part of the section, said central opening constituting the exit passage of the cover section; PA1 the first longitudinal part of the cover section includes a weakened area between the central cut-out and each end edge and is adapted to break when the exit passage in the front face of the casing opens, separating, on the one hand, the channel from the section and, on the other hand, the second longitudinal part from said section.